The present invention relates to high mast lighting systems such as are used on highways and toll plazas.
High mast lighting systems include a vertically elongated central mast or pole surrounded by an annular ring or other shaped platform on which a plurality of light fixtures are mounted. The annular ring is adapted to be raised to the top of the mast and supported there in a locked position during use. A drive mechanism is provided to lower the ring to the base of the mast in order to facilitate maintenance and lamp changes. Typically, the support rings in high mast lighting systems are raised and lowered by the drive means through a plurality of cables secured to the ring and passing downwardly from pulleys on top of the mast into the ring to the drive means.
High mast lighting systems can attain great height, of over 100 feet or more, with the result that they are subjected to severe stresses, particularly during heavy weather. Therefore, it is imperative that the support ring be secured in a fixed position such that it can withstand the great forces to which it is subjected, while at the same time allowing easy maintenance of the system.
A variety of different types of high mast mounting systems have been previously disclosed in, for example, U.S. Pat. Nos. 4,237,530; 4,139,884; 4,851,980; 4,001,573; 3,856,639; and 3,721,816. Certain of these patents disclose latching mechanisms using cooperative cam arrangements for holding the lamp ring or support in its fixed uppermost position. While such devices have been generally satisfactory in use, it is an object of the present invention to provide an improved latching system which is simple in construction, as compared to the prior art, while providing an extremely secure latching arrangement.
Another object of the present invention is to provide a latching arrangement which provides a positive latch that rigidly secures the ring to the mast in its latched position so that weight is relieved from the cables used to raise and lower the ring itself.
Yet another object of the present invention is to provide a latching arrangement with a simple indicating device that provides a positive indication that the ring is latched in position.
A still further object of the present invention is to provide an improved mounting arrangement for lamp fixtures on the support ring of a high mast lighting system.
A still further object of the present invention is to provide an improved ring construction that provides a simple bumper arrangement on the interior of the ring which prevents damage to the ring and the mast during the raising and lowering operation should the mast or ring sway during such operation.